Leading-in conductor



Patented May 1 0, 1932 UNITED STATES PATENT OFFICE I J'OHANNES ANTONIUS MARIA VAN LIEMPT, OF EINDHOVEN, NETHERLANDS, ASSIGNOB TO GENERAL ELECTRIC COMPANY, A CORPORATION 01 NEW YORK LEADING-IN CONDUCTOR Application 1124 larch 13, 1980 Serial No. 485,586, and in the Netherlands November 80, 1929.

The present invention relates to the manufacture of incandescent lamps, electric dischar tubes of the transmitting type, gasfille and vacuum rectifiers X-ra tubes, etc.,

5 and more particularly to the lea g-in conductors of such devices.

When conductors of the usual type are fused in an evacuated glass envelope, there may be air leaka e in the region of each con- LO ductor. This lea age for the most part is believed to be due to the presence of small tears, fractures or fissures residing in the material of the conductor which structural failures cannot always be avoided in the prior art 1 sealing-in wires, notwithstanding the care taken during manufacture of the material. The tears may traverse the conductor material lon 'tudinally or transversely and can nsuall e detected by metallographic meth- BO ods. ading-in conductor material issometimes fabricated. from a base metalsuch as tungsten, molybdenum or zirconium in powdered form and heated to a sintering temperature, simultaneously being pressed to shape after which the body is hammered and drawn.

to wire size. Instead of a wire, the conductor may take the form of a tube which also may be drawn from the pressed and sintered body. Tungsten wire, which is 3 quently used for such material on account of its. favorable coeflicient of expansion when compared to that of Pyrex or other hard glass in which it may be sealed is particulary susceptible to' failure of the crystal or grain structure.

I have discovered and in accordance with my invention that when the various metals or alloys which heretofore have exhibited interstices or other forms of grain discontinuity or deformation are given a special treatment to form the multi-crystal structure into uni-crystalline, i. e. from a miorocrystal to a macrocrystal state, the metal takes on the character of bein strongly resistant to tear and may be satis actorily employed as leading-in conductor material for sealin into a hero-silicate lass. Metal treated in t e manner describe presently is found to have a dense, coherent section which positively pre- 50 eludes gas or air leakage, even after long periods of time. The invention thus has application to all types of high vacuum devices, particularly to the power type which necessitates stems of hard glass, also to gas-filled rectifiers and ordinary incandescent lamps in which air leakage causes substantial reduction of operating life.

Various methods of changing the microcrystalline metallic structure into macrocrystalline are well known in the art, and it will be suilicient to cite as one example the immersion of the sealing-in material in an atmosphere of tungsten chloride (WCI A process of this kind has been described by V an Arkel in the Dutch Journal Physika, 1923, Vol. H, at page 76.

The drawing illustratively exemplifies the application of the invention to a rectifier. In the figure, numeral 1 designates an envelo of boro-silicate glass which may be evacuated or filled with inert gas of suitable pressure, the envelope terminatin in a stem 2. Within the envelope there is a amentary electrode 3 and a cooperating anode 4. Leading-in conductors 5 are sealed in the stem for supplying current to the electrodes. These con uctors may be fabricated of any refractory metals, such as tun sten, molybdenum "or zirconium which has a avorable coefficient of expansion as com ared to that of the glass in which it is sealed and may be treated in any well known and appropriate manner to change the grain structure from the usual microcrystal formation to macrostrystalline.

\Vhat I claim as new and desire'to secure by Letters Patent of the United States is 1. In combination, an evacuated envelope,

a conductor within the envelope and a metallic member sealed in the envelope for supplying current to said'conductor, said member having a uni-crystalline structure whereby gas leakage through the envelope in the region of the metalllc member is prevented.

2. An evacuated envelope terminating in a stem, a conductor within the envelope and a metallic member sealed in said stem for sup lying current to the conductor, said member avin a uni-crystalline structure whereas leaiia e through the stem in the region e meta a member is prevented.

3. An evacuated envelo terminatin in a stem and constituted of oro-silicate' g ass, one or more conductors within the envelo and tungsten wires'sealed in said stem or 5 supplying current to the conductors, said tungsten wires being macrocrystalline.

In witness whereof, I have hereunto set my hand and seal this twentieth day of February, 1930.

10 JOHANNES ANTONIUS MARIA m LIEIPT. 

